The present invention relates to a data storage device and a magnetic disk drive.
Devices using various types of media such as optical disks and magnetic tapes are known as data storage devices. Among them, hard disk drives (HDDs) have become popular as storage devices for computers and they are one of the storage devices indispensable in the current computer system. Further, not limited to computer system, use of hard disks is increasing more and more due to the superior characteristics with the advent of moving picture recording/reproducing devices, car navigation systems, removable memories for digital cameras and so on.
The hard disk drive is provided with a magnetic disk, an actuator and a head. The magnetic disk stores data. The head reads and/or writes data with respect to the magnetic disk. The actuator is driven by a voice coil motor and pivots about a pivot shaft. The actuator causes the head to move radially over the magnetic disk, whereby the head can access a desired track formed on the magnetic disk and perform a data read/write processing.
Various components, including the magnetic disk, are mounted on a base. The base is covered with a top cover. The top cover is screwed to the base. A sealing tape is affixed onto the top cover. An example of such a hard disk drive is disclosed in Japanese Patent Laid Open No. Hei 11-232833 (Patent Literature 1). The hard disk drive disclosed in Patent Literature 1 is shown in a sectional view of FIG. 5.
In the hard disk drive shown in FIG. 5, which is indicated at 900, a stepped surface 920 is formed inside a base 910. A screw 940 is threadedly fitted in the stepped surface 920 from the top cover 930 side. The screw 940 is secured to a concave portion 950 which is depressed from a surface of the top cover 930. With the top cover 930 thus screwed to the base 910, an upper surface of an outer periphery of the base 910 and the surface of the top cover 930 are approximately flush with each other.
The whole of the top cover 930 screwed to the base 910 is covered with a sealing tape 960. The sealing tape 960 covers the whole periphery of an open edge of the base 910 and seals a seam 911 between the base 910 and the top cover 930 hermetically. As a result, the top cover 930 is confined inside the sealing tape 960, and the screw 940 and a through hole 970 for fixing the top cover 930 are also enclosed inside the sealing tape 960. Consequently, the generation of an air current in the seam 911 between the base 910 and the top cover 960 and resultant oscillation of air are prevented and noise is suppressed.
As another example, a hard disk drive which prevents the entry of outside air into the inside of a base is disclosed in Japanese Patent Laid Open No. Hei 10-334641 (Patent Literature 2). This hard disk drive is not shown. A thin top cover formed by press working is used in the hard disk drive disclosed in Patent Literature 2. The top cover is fitted inside an inner periphery surface of a base and is screwed from above to the base located below the top cover in this state. A tapping hole formed on the top cover side for threaded engagement therewith of a screw is formed in a clamping surface lower than the top cover surface to prevent projection of a head of the screw from the top cover surface.
A sealing tape is affixed onto the top cover from above the tightened screw. The affixed sealing tape covers the top cover surface completely and also covers the tightened screw. Further, the sealing tape completely closes a gap formed between the base and the top cover to prevent the entry of outside air into the base through the gap. In this hard disk drive, a packing is sandwiched between the base and the top cover to keep the inside of the base in a hermetically sealed condition.
A minidisk read/write apparatus is disclosed in Japanese Patent Laid Open No. 2000-234650 (Patent Literature 3). In this patent literature, a structure wherein a cover (a deck-side frame) is screwed to a chassis from below is disclosed in the minidisk read/write apparatus. More specifically, a shaft portion of a screw for fixing the cover is disposed at a predetermined gap from a through hole formed in the chassis without contact with the through hole. Further, a head of the screw is disposed at a predetermined gap from a fitting hole without contact with the fitting hole having larger diameter than the through hole. Thus, the screw is mounted spacedly from and without contact with the chassis. If the cover and the chassis oscillate in the gap between the screw head and the chassis, the oscillation is absorbed by an elastic rubber member. Thus, the read/write apparatus disclosed in Patent Literature 3 has a structure wherein the screw, especially the screw head, and the chassis are spaced from each other.
For tightening the screw positively when the top cover is screwed to the base, the larger number of screw threads on the side face of the tapping hole is preferable. In each of the hard disk drives disclosed in Patent Literatures 1 and 2, the screw for fixing the top cover is threadedly engaged with the base from the top cover side. In case of forming the base by die casting, the base can be formed thick unlike press working, so that a tapping hole can be formed deep in the base and hence it is possible to increase the number of screw threads on the side face of the tapping hole.